1. Field of the Invention
The present invention generally relates to an apparatus and method for protecting fluid systems against damage from the expansion of freezing aqueous solutions contained or transported within said fluid systems. The invention also describes the specific properties of said apparatus that help to ensure its effectiveness.
2. Description of the Prior Art
When water freezes within a confined space, it is well known that the 9% coefficient of thermal expansion occurring during the phase shift of water between liquid and solid results in extreme pressures being exerted upon apparatuses and assemblies of fluid systems, particularly those containing or transporting aqueous fluids or solutions.
In U.S. Pat. No. 318,856, to Bilz, it was proposed that a series of cork rings be sequentially inserted within a pipe to form a liner, allowing for the expansion of freezing water within the pipe. This art fails to account for the fact that cork is a natural material that degrades and decomposes rather quickly, the process of which poses the threat of fragmentation of the material and clogging of the pipe over time. This prior art also fails to disclose a means of protecting anything other than a pipe, such as a vessel, plenum, manifold or container.
In U.S. Pat. No. 596,062, to Firey, it is proposed that a core of either rubber or metal be disposed within a pipe to prevent rupture caused by freezing water within the pipe. This art is deficient in that a metal core would elastically deform under the pressure of a single freeze and wouldn't be able to return to its original shape or dimensions, thereby failing to repeatedly protect the pipe during subsequent freezes. Additionally, Firey discloses either a hollow rubber core or a solid rubber core to be placed within the pipe to offer protection to the pipe from freezing. The rubber cores mentioned by Firey are not described as to their properties, as it is now known by those skilled in the art that solid rubber will not compress in the manner necessary to perform the intended function. A hollow rubber core is essentially a tube, and is rendered useless if a shard of ice penetrates the tube and allows water to enter into the hollow space within. In addition, the hollow tube will fill with water unless the ends are somehow sealed either during installation or during manufacture. If the ends are sealed during manufacture, then the hollow core must be made to predetermined lengths, making it difficult to use in a wide variety of applications. These embodiments also fail to describe a means of protecting anything other than a pipe, such as a vessel, plenum or container of any sort.
In U.S. Pat. No. 926,092, to Bright, it was disclosed that a core of metallic material is surrounded by a resilient covering, and is then inserted into a length of pipe in order to protect the pipe from the damaging effects of freezing water contained in the pipe. Bright claims that the coefficient of elasticity of the resilient material will offer protection to the pipe under the expansive pressures of the freezing water contained therein. However, it is well known by those skilled in the art that solid rubber, although elastic, will not compress but will instead deflect, and will occupy the same volume of space, resulting in a failure of the pipe or a fitting. Bright also fails to disclose any of the properties of the resilient covering, which is key to its performance. Bright also fails to describe a means of protecting anything other than a pipe, such as a vessel, plenum or manifold or container.
In U.S. Pat. No. 4,651,781, to Kandleman, it was proposed that an inner tube is supported in a closed-cell, plastic foam shell, both being supported in a tubing member serving as containment piping. This art is designed for use as an accumulator in a hydraulic system for attenuating pressure surges and doesn't describe a method of freeze protection.
In U.S. Pat. Nos. 5,538,043 and 6,009,906 to Salazar, it was proposed that a flexible, resilient, compressible trunk be employed within a pipeline in order to absorb the expansion pressure of fluid within said pipeline. However this prior art fails to adequately describe the properties of the material that is to be placed within the pipeline. Not every resilient, flexible, compressible material will adequately perform the intended task. There are specific characteristics of the material that will determine its effectiveness, such as the closed-cell configuration of the foam. Even closed-cells outside of a specific size range tend to absorb water under the extreme pressures exerted on the material during freeze conditions. Is also known to those skilled in the art that the hardness of the material must be within a specific range and experiments have revealed that there is a high likelihood of failure if the properties of the material do not meet strict criteria. Additionally, this prior art discloses that the material will not impart impurities into the transported fluid. However, through leachability testing it is known by those skilled in the art that most polymers will leach particulates of their compositional makeup into the surrounding fluid, particularly at high temperatures. This can pose a problem in systems that are sensitive to impurities or such as potable water systems or sensitive fluid systems found in scientific and industrial equipment. Furthermore, this prior art is limited in its application. The prior art specifies the use of the material in pipelines, tubes and conduits, yet there is no mention of a method or apparatus for protecting other types of vessels or containers.
The disadvantages inherent to these apparatuses and methods limit their viability by either being incomplete in their explanation of how to make and use or are unreliable and ineffective. Existing freeze protection methods and apparatuses are deficient in providing a means of reliably and repeatedly protecting fluid systems from damage to components during a freeze of the system.